1. Field of the Invention
The present invention relates to a ferroelectric thin film and a method for forming the same. More particularly, the present invention relates to a ferroelectric thin film suitable for electronic devices such as integrated, non-volatile memory devices, and a method for forming the same using a sol-gel process.
2. Description of the Related Art
A ferroelectric memory device works based on the ferroelectric properties of a ferroelectric thin film and has the structure of a non-volatile memory which does not require back-up power. Ferroelectric materials for ferroelectric memory devices are required to have a high residual polarization and a low coercive field. Furthermore, in addition to a low leakage current in order to obtain good electric properties, the polarization fatigue caused by periodic polarization switching must be reduced. With respect to reduction of a core voltage and high integration, ferroelectric thin films are required to have a thickness of less than several hundreds of nanometers.
A ferroelectric material mainly used for ferroelectric memory devices is lead zirconate titanate (PZT), which has a high residual polarization in a bulk state. Recently, an oxide material of a catalyst material containing one or more selected from Si, Ge, and Sn in PZT was developed.
A PZT thin film may be formed by a sol-gel process as shown in FIG. 1. However, the composition, i.e., a mixture of a PZT solution and a Bi2SiO5 solution for forming an oxide thin film as shown in FIG. 1, has very poor storage stability. In addition, an oxide thin film formed by coating and heat treatment of the composition restricts the selection of an electrode to be formed under the oxide thin film. For these reasons, such a PZT thin film is not currently used.